SU1668646A1 - Acid treatment of producing formation - Google Patents

Abstract

The invention relates to the oil industry, in particular to methods of acidizing productive formations. The purpose of the invention is to reduce the corrosion of downhole equipment. Hydrochloric acid solution and buffer fluid are pumped into the formation through the well. After injection of these agents in the well, they create a periodic alternation of constant-largest depressions with repressions, the depression time being determined from the ratio T = V / Q, where Q is the formation flow rate for a given depression

V is the volume of buffer fluid, and the time of repression is equal to the time of pushing into the reservoir the volume of buffer fluid recovered during the depression. 1 il.

Description

The invention relates to the oil industry, in particular to methods of acidizing productive formations.

The purpose of the invention is to reduce the corrosion of downhole equipment.

The method is carried out by arranging the tubing string shown in the drawing.

On the tubing-1 down the packer 2 and the pipe, including the jet pump 3, the Central passage channel 4.

Through the tubing is pumped into the perforation interval, the calculated volume of acid and buffer fluid. Packer 2 is unpacked. The annulus is closed and an acid solution and a buffer fluid are forced into the reservoir. On the cable 5 down the remote pressure gauge 6 and placed above it a sealing node 7.

The pressure gauge 6 is installed above the perforation interval, while the sealing unit 7 closes the central passage channel 4.

By pumping the working fluid into the tubing, through the jet pump into the annulus create under the packer the maximum possible depression. The pumping of the fluid is carried out by ground pumping units. At the same time, the vacuum created under the packer is regulated by the flow rate of the fluid through the jet pump and is monitored by a remote pressure gauge 6.

After the injection of the acid and the buffer fluid into the reservoir, a periodic alternation of permanently largest depressions with repressions is created, the duration of the depressions is determined by the formula

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where Q is the production rate of the reservoir at a given depression, V-volume of buffer fluid pressed into the reservoir after acid, and the time of action of repression is the time required for pushing into the reservoir extracted during the period of depression of the volume of buffer fluid.

The maximum possible depression is the maximum depression that can be created in specific geological and technical conditions. In the absence of any geological and technical constraints, this is depressed, equal to the reservoir pressure.

The flow from the reservoir is established by changing the level of fluid in the measuring tank, to which the suction and discharge sleeves of pumping units are connected.

When the inflow from the reservoir, equal to the volume of previously buffered buffer fluid, close the annulus and push the evacuated volume into the reservoir.

The cycle described is repeated over the estimated reaction time of the acid with the rock.

By creating a long-lasting depression, the reaction products are pumped out of the reservoir and the well is developed.

Advantages of the method:

- creating the maximum possible depression provides the maximum speed of acid in the reservoir, which eliminates the reduction in the rate of acid-rock reaction due to its stagnation;

- during the contact of the rock with the acid equally in the entire volume of the near-wellbore zone being treated;

- Provides conditions for the full and uniform production of the total injected volume of acid;

- during the depression only the buffer fluid is pumped out; the casing and equipment are not exposed to the acid during its reaction with the rock.

An example. The well opened the reservoir at a depth of 3020-3028 m. The production column with a diameter of 146 mm, wall thickness of 8 mm was lowered to a depth of 3065, the maximum angle of inclination was 28 °, determined by a pressure of 12 MPa, the well was put into operation with an initial production rate of 35 tons / day anhydrous oil, after 14 months. work rate decreased to 5 tons / day., reservoir pressure 24 MPa. For the acid treatment, the layout was lowered into the well: a funnel - to a depth of 3000 m, a packer - to a depth of 3009 m, a jet pump with a diameter of 115 mm with a central passageway with a diameter of 50 mm - on 3008 m, tubing

diameter 62 mm - up to the mouth; the mouth is equipped with fountain fittings. 5 m3 of 10% hydrochloric acid solution and 0.5 m3 of buffer-unicol were pumped into the formation interval.

U-2. Unpacking was carried out, closing the aperture, pushing acid and buffer into the formation, after which the annulus was opened. On the geophysical cable, the pressure gauge with the overhead gauge was lowered into the perforation interval

0 sealing unit. In this case, the sealing unit blocked the central passage of the pump. By pumping two aggregates of salt solution in the tubing through the pump into the annulus, a pressure of 12 MPa was created under the packer (while the load on the casing was 24-12 12 MPa, which does not exceed the pressure of the casing pressing). The pressure under the packer was controlled using a pressure gauge and

0 was regulated by decreasing the pressure of pumping units at the mouth. Saline solution was fed into the well and out of it in a closed cycle, which allowed determining the inflow from the well by changing the level of liquid in

5 containers.

At the first cycle of the depot session, the inflow from the well amounted to Q 0.025 m3 / min, which allowed determining the duration of the depression.

1 0b25 20 min. The annulus was closed and, with a pressure at the mouth of 12 MPa, they pushed 0.5 m of salt solution into the well, the time required

5 for a roll, made 16 min.

Spent eight cycles of depression-repression as described above. At the same time, the time of depression decreased to 12 minutes, and the time of depression - to 10 minutes. On virgin

In the cycle, the time of depression and repression did not decrease, making 12 and 10 minutes respectively, which made it possible to conclude that the reaction of the acid with the rock was practically stopped. Therefore, time

5, the effect of acid on the column and depth equipment is less than that of the prototype method, i.e. reduced corrosive effect of acid on downhole equipment.

0

Claims (1)

Invention Formula A method of acidizing a productive formation, consisting in pumping an acid solution and a buffer fluid into the formation with varying pressure, characterized in that, in order to reduce corrosion of the well equipment, after injection of the acid solution and the buffer fluid into the formation in the well create a periodic alternation of the largest possible depressions with repressions, and the time of depression is determined from the ratio  - where Q is the formation flow rate for a given depression, V is the volume of the buffer fluid, and the time of repression is equal to the time of pushing the volume of buffer fluid extracted into the reservoir for the period of depression.